1. Field of the Invention
This invention relates to electromagnetic driving devices for cameras in which the direction of movement of a driven member is reversed by changing the direction of current flow to a coil arranged in the magnetic field, and more particularly to electromagnetic driving devices for cameras in which the focus adjusting operation and the exposure operation are controlled by selectively utilizing the directions of movement of the aforesaid driven member.
2. Description of the Prior Art
In the past, the camera having the automatic focus adjusting mechanism (hereinafter described as AF mechanism) with the automatic exposure control in accordance with the object brightness was necessarily provided with a 1st electromagnet for controlling the initiation and termination of an operation of the AF mechanism and a 2nd electromagnet for controlling the opening and closing operation of the shutter blades. This constituted a drawback that the internal structure of the camera became complicated and it was disadvantageous from the cost standpoint. Therefore, of recent years, it is strongly desired to make such camera operation controllable by using one electromagnet.
On the other hand, it is known in the art to provide a camera using one electromagnet in combination with a coordinating system for the AF mechanism and the shutter, as, for example, disclosed in Japanese Laid-Open Patent Application No. Sho 54-71633 (U.S. Pat. No. 4,209,242). This camera has to actuate and release the AF mechanism and the shutter in such a manner that an energization of the electromagnet stops the AF mechanism, and the subsequent deenergization of the electromagnet closes the shutter blades, while the start of movement of the AF mechanism and the opening of the shutter are carried out by a moving member which starts to run from the latched position when a camera release is actuated. With such coordinating system, however, the moving member after having been taken out of the latching connection in response to actuation of a camera release is allowed to govern its movement all the way in no relation to the operation of the electromagnet with the result that the operation of the AF mechanism is initiated and the shutter blades are opened. Therefore, there has been a high possibility of occurrence of a faulty operation, for example, a premature opening of the shutter blades before the termination of the focus adjusting operation, and it has been difficult to expect an accurate and reliable control. Also, since, in such camera, the actuation of camera release is followed after a predetermined time, this is, soon after the termination of the focus adjusting operation, by the opening of the shutter, a self-timer shot is impossible. This has been disadvantageous for the broadening of shooting capabilities of the camera is limited.
Also, the use of such mechanical linkage between the actuator for the AF mechanism and the actuator for the camera release gives rise to another problem that as the release button is pushed down very fast, the electrical preparation for the AF mechanism cannot catch up with the start of movement of the AF mechanism. To solve this, it is unavoidable to increase the complexity of structure.